Development of expert system knowledge base to on-line diagnosis of rotor electrical faults of induction motors

The authors consider the development of a knowledge base branch related to rotor electrical faults in squirrel cage machines, to be implemented in an expert system (ES), utilizing instantaneous values as input data. The knowledge base is organized in two levels: in the first level diagnostic indexes for the orientation of the ES inference engine toward the appropriate branch of the fault tree are utilized. The second level includes the deep knowledge with a data set obtained on the basis of a complete faulty machine model. The diagnostic indexes of the first level concern how to distinguish faulty events from the healthy signals due to the unavoidable manufacturing asymmetries. They are pointed out through a simplified model of a faulted rotor that needs few machine parameters. Some diagnosis examples are reported to describe the sequence of operations of the diagnostic system